1. Field of the Invention
The present invention relates to an apparatus for repeatedly recording and reading the radiation image information of a subject on and from a stimulable phosphor sheet housed in the apparatus.
2. Description of the Related Art
There is known a system for recording radiation image information of a subject such as a human body with a stimulable phosphor, and reproducing the recorded radiation image information on a photosensitive medium such as a photographic film, or displaying the recorded radiation image information on a display device such as a CRT or the like.
The stimulable phosphor is a phosphor which, when exposed to an applied radiation (X-rays, .alpha.-rays, .gamma.-rays, electron beams, ultraviolet radiation, or the like), stores a part of the energy of the radiation, and, when subsequently exposed to applied stimulating rays such as visible light, emits light in proportion to the stored energy of the radiation. Usually, a sheet provided with a layer of the stimulable phosphor, or a stimulable phosphor sheet, is used for easy handling.
The above known system includes a built-in radiation image information reading apparatus which comprises an exposure unit for recording radiation image information of a subject on a stimulable phosphor sheet, an image information reading unit for applying stimulating rays to the stimulable phosphor sheet with the recorded radiation image information to photoelectrically reading the recorded radiation image information, and an erasing unit for erasing remaining image information from the stimulable phosphor sheet after the recorded image information has been read. The stimulable phosphor sheet is circulated or moved back and forth in the built-in radiation image information reading apparatus.
FIG. 5 of the accompanying drawings shows an internal structure of a general radiation image information reading apparatus 1. As shown in FIG. 5, the radiation image information reading apparatus 1 has an exposure unit 2 for temporarily recording radiation image information of a subject on a stimulable phosphor sheet S, an image information reading unit 3 for applying a laser beam L as stimulating rays to the stimulable phosphor sheet S to photoelectrically reading the recorded radiation image information, an erasing and feeding unit 4 for erasing remaining image information from the stimulable phosphor sheet S after the recorded image information has been read, a circulatory feed system 5 for circulating the stimulable phosphor sheet S, and a stacker 7 for placing therein a magazine 6 which houses the stimulable phosphor sheet S.
The image information reading unit 3 has an auxiliary scanning feed system 8 for feeding the stimulable phosphor sheet S in an auxiliary scanning direction indicated by the arrow A, an optical system 9 for applying the stimulable phosphor sheet S being fed in the auxiliary scanning direction in a main scanning direction substantially perpendicular to the auxiliary scanning direction, and a light guide system 10 for photoelectrically reading light emitted from the stimulable phosphor sheet S when the laser beam L is applied thereto.
In the image information reading unit 3, the stimulable phosphor sheet S is fed horizontally in the auxiliary scanning direction indicated by the arrow A. Therefore, the image information reading unit 3 is considerably elongate in the horizontal direction. Accordingly, the radiation image information reading apparatus 1 has a considerably large depth in the direction indicated by the arrow D.